See below - follow the link for further information and replacement details. The battery in my 6230i is one of those affected.....
Dear Nokia Customer,
This is a product advisory for the Nokia-branded BL-5C battery manufactured by Matsushita Battery Industrial Co. Ltd. of Japan between December 2005 and November 2006. This product advisory does not apply to any other Nokia battery.
Nokia has identified that in very rare cases the affected batteries could potentially experience over heating initiated by a short circuit while charging, causing the battery to dislodge. Nokia is working closely with relevant local authorities to investigate this situation.
Nokia has several suppliers for BL-5C batteries that have collectively produced more than 300 million BL-5C batteries. This advisory applies only to the 46 million batteries manufactured by Matsushita between December 2005 and November 2006. There have been approximately 100 incidents of over heating reported globally. No serious injuries or property damage have been reported.
Consumers with a BL-5C battery subject to this advisory should note that all of the approximately 100 incidents have occurred while charging the battery. According to Nokia's knowledge this issue does not affect any other use of the mobile device. Concerned consumers may want to monitor a mobile device while charging that contains a BL-5C battery subject to this product advisory.
While the occurrence in the BL-5C batteries produced by Matsushita in the time-period specified is very rare, for consumers wishing to do so, Nokia and Matsushita offer to replace any BL-5C battery subject to this product advisory.
The BL-5C batteries which are subject to the product advisory were used with the following Nokia models or separately as accessories:
Nokia 1100, Nokia 1100c, Nokia 1101, Nokia 1108, Nokia 1110, Nokia 1112, Nokia 1255, Nokia 1315, Nokia 1600, Nokia 2112, Nokia 2118, Nokia 2255, Nokia 2272, Nokia 2275, Nokia 2300, Nokia 2300c, Nokia 2310, Nokia 2355, Nokia 2600, Nokia 2610, Nokia 2610b, Nokia 2626, Nokia 3100, Nokia 3105, Nokia 3120, Nokia 3125, Nokia 6030, Nokia 6085, Nokia 6086, Nokia 6108, Nokia 6175i, Nokia 6178i, Nokia 6230, Nokia 6230i, Nokia 6270, Nokia 6600, Nokia 6620, Nokia 6630, Nokia 6631, Nokia 6670, Nokia 6680, Nokia 6681, Nokia 6682, Nokia 6820, Nokia 6822, Nokia 7610, Nokia N70, Nokia N71, Nokia N72, Nokia N91, Nokia E50, Nokia E60 http://www.nokia.com/batteryreplacement/en/